Small energy providers have added to the pressure on the 'big six' suppliers to hold prices with the launch of a fixed-rate deal from Co-op Energy and price freezes by green energy firms Ecotricity and Good Energy.

In a week when price rises in the region of 10% are being implemented by British Gas and npower, Ecotricity said its customers would not see bills rise until at least April 2014, extending a previous promise not to raise tariffs until the new year. The deal applies to its electricity and gas tariffs.

Ecotricity said that by creating its own green energy sources it had "reached a degree of energy independence" which allowed it to undercut the standard tariffs of the big six.

It generates around 40% of its own electricity through green sources and said it had planning permission for enough new sources to double that.

Its founder, Dale Vince, said: "We now produce around 40% of our own electricity through our own green sources, and the more we build the better able we are to shield our customers from price hikes that come with a reliance on the fossil fuel market.

"That's the way Britain has to go, because only energy independence can properly tackle rising fuel bills. The alternative is where we are now – a continuing reliance on fossil fuels, ever-increasing energy bills, and more people falling into fuel poverty every year."

Its chief executive, Juliet Davenport, said: "Good Energy has taken the decision to hold prices as the majority of its external costs are not rising until 1st April 2014 … We know our customers appreciate price stability and today's news will help them plan their energy expenditure over the coming winter months."

The tariffs will protect customers from price increases for up to two years, but have no exit penalties, so if energy costs do come down people can switch away to a cheaper deal.

The Fixed March 2015 tariff will be the cheapest fixed-price plan on the market, costing the average household £1,168 a year for gas and electricity, according to price comparison site uSwitch.

Co-op customers can also receive a share of profits twice a year if they sign up to membership.

Ramsay Dunning, group general manager at Co-operative Energy, said: "Not only will customers be assured their prices are fixed, if they sign up to any of our tariffs and become a member they will also benefit from a share of profits twice a year and have a say in how their energy company is run, so they will know for sure they're getting the very best deal."

After that, the cheapest deals are from Co-op, then two other small providers, Ovo and First Utility.

Tom Lyon, energy expert at uSwitch.com, says: "To see another small supplier at the top of the best buy table is fantastic news and a welcome indication of what real competition could achieve in this market.

"The deals are there and it's in the hands of consumers to snap them up and fan the flames of competition. Only with a healthy competitive market will we see suppliers battle it out to offer the cheapest plans, superior services and to drive costs and inefficiencies down."